A bill in Congress would require the federal government to study the full costs and benefits of Gov. Jerry Brown's twin tunnels plan - something the state has said it will not do.

U.S. Rep. John Garamendi, a Democrat from Walnut Grove who opposes the plan and is running for re-election, said he hopes to appeal to fiscal conservatives in the GOP-controlled House of Representatives.

Similar legislation at the state level by Assemblyman Bill Berryhill, a Republican from Stockton, failed earlier this year.

"If they're going to build something, what's it going to cost and what's the benefit?" Garamendi said last week. "This is something the Republicans scream they've got to have on every project - 'Do a cost-benefit analysis.' OK, we agree. Let's do it."

Garamendi authored the bill along with Democrats Jerry McNerney, George Miller, Mike Thompson and Doris Matsui.

Brown's plan, known as the Bay Delta Conservation Plan, would pipe Sierra snowmelt toward San Joaquin Valley farms and Southern California cities. Less water would flow through the Delta.

The cost of the tunnels has been estimated at $14 billion, with billions more needed to restore Delta habitat. Officials are also calculating the potential benefits for those who receive the water and would have to pay for the tunnels.

However, no broader statewide analysis of all costs - social, environmental and financial - has been undertaken.

Garamendi's HR6484 requires the U.S. Secretary of the Interior to conduct such a study and report back by June. The bill also requires officials to study at least one solution that does not involve building the tunnels.

Those who would receive the water have said a cost-benefit study is not necessary, because the project already must go through what they consider a rigorous process of analysis and approval.

Garamendi said he believes they don't want a study done because the results will not support their cause.

"This project will have to be sold to the farmers and the Southern California urban water users, and they're going to find out it's going to be extremely expensive water," Garamendi said.

Tom Zuckerman, an attorney for central Delta farmers, said south-state interests will try to "squash" the bill as they did in the Legislature but said the difference is those interests are proportionately less numerous in Congress. "It's worth a try, I think," he said.

Officials say some water will continue to be sent through the Delta even if the tunnels are built, so Garamendi's bill also calls for the U.S. Bureau of Reclamation to assist in maintaining the levees that are needed to securely convey that water. Most maintenance today is paid for by local landowners and by the state, despite that the federal Central Valley Project relies on the levees, too.

The Bureau of Reclamation said Friday that it has no position on Garamendi's bill.